#define _CRT_SECURE_NO_WARNINGS 1
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* pruneTree(TreeNode* root) {
        _pruneTree(root, nullptr);
        if (root->left == nullptr && root->right == nullptr && root->val == 0) root = nullptr;
        return root;
    }
    void _pruneTree(TreeNode* root, TreeNode* parent)
    {
        if (root == nullptr) return;

        _pruneTree(root->left, root);
        _pruneTree(root->right, root);
        if (root->left == nullptr && root->right == nullptr && root->val == 0)
        {
            if (parent == nullptr) return;
            if (parent->left == root) parent->left = nullptr;
            else parent->right = nullptr;
            return;
        }
    }
};

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* pruneTree(TreeNode* root) {
        if (root == nullptr) return nullptr;

        root->left = pruneTree(root->left);
        root->right = pruneTree(root->right);
        if (root->left == nullptr && root->right == nullptr && root->val == 0) root = nullptr;
        return root;
    }
};